Vinyl sulfonamide-acrylonitrile copolymers



United States Patent VINYL SULFONAMH)E-ACRYLONITRILE COPOLYMERS HaroldF. Park, East Longmeadow, and Robert M. Dickey, Wilbraham, Mass.,assignors to Monsanto Chemical Company, St. Louis, Mo., a corporation ofDelaware No Drawing. Application May 1, 1953,

Serial No. 352,591 a 3 Claims. (Cl. 26079.3)

This invention relates to new fiber-forming copolymers. Moreparticularly, this invention relates to new copolymers of acrylonitrilethat are useful in thepreparation of readily dyeable fibers.

This application is a continuation-in-part of application Serial No.274,515 filed March 1, 1952, now abandoned.

Acrylonitrile has many unique properties not possesse'd by most vinylmonomers. It may be reacted with unsubstituted amides to formcyanoethylation addition products or with ethylenically unsaturatedcompounds in order to form copolymers. When the compound to be reactedwith acrylonitrile contains both an amide radical and an ethyleneradical, the nature of the product will depend upon the relativereactivity of the amide radical. Unsubstituted amide radicals tend toreact readily with acrylonitrile to form cyanoethylation products. Thetendency towards cyanoethylation is much reduced in the case of themono-N-substituted amides and substantially no cyanoethylation willoccur in the case of the disubstituted amides. Thus, acrylonitrile willreact with formamide to form a cyanoethylation product but will notreact with dimethyl formamide.

It is known that unsubstituted acrylonitrile will react withN-substituted vinyl sulfonamides to form copolymers and that certainclasses of substituted acrylonitrile monomers will react withunsubstituted vinyl sulfonamide to form copolymers but, heretofore, ithas not been possible to prepare copolymers of unsubstitutedacrylonitrile and unsubstituted vinyl sulfonamide. Vinyl sulfonamidecontains an NH2 radical directly coupled to an electrophilic sulfonylradical. As a result when unsubstituted vinyl sulfonamide is reactedwith unsubstituted acrylonitrile, the normal tendency is for theacrylonitrile to react with the NH2 group of the vinyl sulfonamide inorder to form a cyanoethylation product.

Accordingly, an object of the present invention is the provision ofcopolymers of acrylonitrile and unsubstituted vinyl sulfonamide.

Another object is the provision of a process for'copolymerizingacrylonitrile with unsubstituted vinyl sulfonamide.

A further object is the provision of new synthetic fibers.

These and other objects are attained by reacting acrylonitrile withvinyl sulfonamide in a liquid medium having a pH of from 3.0 to 8.0.Fibers are prepared by dis solving the copolymer ina suitable solventand spinning the solution in order to form filaments that can be formedinto fibers. If desired, the copolymers can. be crosslinked by reactionwith formaldehyde, a polymer thereof or hexamethylene tetramine, suchcross-linked polymers forming much stronger filaments. The reaction withthe cross-linking agent can be conducted either before or afterfilaments have been formed. a

The following examples are given in illustration and are not intended aslimitations on the scope of this in-' Patented Aug. 28, 1956 vention.Where parts are mentioned, they are parts by weight.

Example I Add 0.1 part of the sodium salt of octadecyl naphthalenesulfonic acid and 0.01 part of potassium persulfate to 200 parts ofwater. The pH of the resulting solution will be about 7. Slowly add amixture of parts of acrylonitrile and 10 parts of vinyl sulfonamide withconstant agitation. Throughout the addition of the monomer mixture,maintain the aqueous solution at reflux temperature and atmosphericpressure. After all of the monomer is added, continue the agitation andthe heating under reflux for about one hour. The product is a granularsuspension of a copolymer of acrylonitrile and vinyl sulfonamidecontaining approximately 90 parts by weight of acrylonitrile and 10parts by weight of vinyl sulfonamide. The copolymer may be recovered byfiltration and may be freed from emulsifying agent and catalyst residuesby washing with water. The copolymer is substantially insoluble in waterbut is soluble in many organic solvents such as formamide, acetamide,dialkyl formamides, dialkyl acetamides, dimethyl carbamyl compounds,cyanomethyl compounds, etc. Solutions of the copolymers may be used forpreparing films, fibers, filaments, etc. by extruding the solutions intoa coagulative medium or an evaporative atmosphere.

Example 11 Add about 0.5 part of the sodium salt of dioctylsulfosuccinic acid and about 0.3 part of potassium persulfate to 200parts of water. The pH of the resulting solution will be about 6. Slowlyadd a mixture of 99 parts of acrylonitrile monomer and 1.0 part of vinylsulfonamide monomer with constant agitation. Maintain the solution underconstant agitation at reflux temperature and atmospheric pressurethroughout the addition of the monomer mixture and for about one hourthereafter. The product is an aqueous suspension of a copolymer of 99parts of acrylonitrile and 1.0 part of vinyl sulfonamide.

The copolymer may be recovered by filtration and puri- Example III Heat1000 parts of freshly distilled dimethyl formarnide to a temperature ofabout 100 C. and dissolve therein about 90 parts of acrylonitrile, 10parts of vinyl sulfonamide and 0.5 part of acetyl peroxide. Theresultant solution issubstantially neutral. Maintain the solution at atemperature of about 100 C. for a period of 24 hours. At the end of thistime, substantially all of the acrylonitrile has copolymerized withsubstantially all of the vinyl sulfonamide, the copolymer containingabout 90 parts of acrylonitrile and 10 parts of vinyl sulfonamide. Theproduct is a viscous gel.

If the acetyl peroxide of the preceding example is replaced by sodiumethylate, the product will not be a copolymer but will consistessentially of the cyanoethylation product of acrylonitrile and vinylsulfonamide.

Example I V Extrude the viscous gel obtained as the product of Ex ampleI'II through a six-denier spinneret into a coagulating bath of acetonein order to form filaments. Pass the resultant filaments through anatmosphere saturated with formaldehyde vapors at a temperature of C. andthen through a heating zone to remove excess formaldehyde. Theacrylonitrile-vinyl sulfonamide copolymers are cross-linked as a resultof the treatment with formaldehyde and 'the tensile strength and heatdistortion temperature of the filaments is greatly increased.

The starting materials for the present invention are monomericacrylonitrile and monomeric vinyl sulfonamide. Acrylonitrile is awell-known compound commercially available in large amounts. Vinylsulfonamide may be prepared by the dehydration of thearnmonium saltofvinyl sulfonamide as shown in co-pending application Serial No. 274,514filed March 1, '1952 in the name of Harold F. Park.

The copolymers of the present invention areprepared by copolymerizing amixture of from 85 :to 99 parts of acrylonitrile and from to 1 parts ofvinyl sulfonamide in a liquid medium ata pH of from 3.0 to 8.0. Theliquid medium should be water or a polar organic solvent vthatisnon-reactive with acrylonitrile and vinyl ssulfonamide. Acrylonitrilewill react with many polarlorganic solvents under either basic or acidicconditions and sometimes both in order to form cyanoethylation products.Therefore, some care should be exercised in selecting the solvent.Generally speaking, the operable organic solvents are the polar or anicsolvents for acrylonitrile that are non-reactive therewith under the pHconditions employed. Among the solvents that may be used at any pHwithin the range of from about 3.0 to 3.8 are the dialkyl formamides,dialkyl sulfones, dialkyl acetamides, etc; representative solventsincluding dirnethyl formamide, dimethyl sulfone, dioxane, ethylenecarbonate, N-forma-l morpholine, etc. Other suitable solvents that arepreferably used only under acidic conditions include the aliphaticalcohols,especially the lower aliphatic alcohols having from 1 to 4carbon atoms, methyl carbarnate, malonitrile, etc.

The vinyl sulfonamide-acrylonitrile copolymers are substantiallyinsoluble in water and are also relatively insoluble in many of thepolar organic solvents in which the monomers are soluble, e. g., thealiphatic alcohols, dioaane, etc. However, the copolymers are soluble insubstantially all of the organic solvents used for dissolvingpolyacrylonitrile, such solvents including the dialkyl sulfones, dialkylformamides, dialkyl acetamides, dimethyl carbamyl compounds, cyanomethylcompounds, etc.

By judicious selection of the solvent for the polymerization reaction,it is possible to obtain the copolymers at the end of the reaction in awide variety of physical conditions. Thus, solvent for the copolymer maybe used as the solvent for the monomer mixture as in Example III, inwhich case a solution of the copolymer is obtained when the reaction iscomplete. Such solutions may be spun into filaments without furthertreatment as shown by Example 1V. if desired, a non'solvent for thecopolymer may be used as the solvent for the monomer mixture and if suchis the case, a suspension of the copolymer will be obtained at the endof the reaction. When a non-solvent for the copolymer is used as thesolvent for the monomer mixture, the particle size of the copolymers canbe regulated through the addition of an emulsifying or suspending agentas in Examples 1 and ll.

Any suitable emulsifying or suspending agent or both may be used inplace of the sodium octadecyl naphthalene sulfonate and sodium dioctylsulfosuccinate of Examples I. and ll. Sui-table emulsifying agentsinclude the alkyl sulfonates, aryl sulfonates, aralkyl sulfona-tes,etc., nonionic emulsifying agents such as alkylene oxide condensationproducts, etc., cationic emulsifying agents such as cetyl benzyldimethyl ammonium chloride, lauryl triethyl ammonium acetate, etc. Amongthe suspending agents that may be used are aluminum hydroxide, calciumphosphate, etc. The amount of such agents may be-varied as required fromabout 0.01 to 5.0% by weight based on the monomer mixture.

The polymerization reaction may be conducted at any temperature fromroom temperature to about 175 C. The reaction proceeds more smoothly andis easier 'to control when temperatures of from about 50 to 100 C. areused.

The polymerization reaction is preferably accelerated through the use ofa suitable polymerization catalyst alabsence-of such catalysts. "Thecatalyst shouldbe soluble in the solvent for the monomer mixture. Amongthe catalysts that are soluble in water, polar organic solvents or bothare azo compounds, peroxides, per salts, etc. including the salts ofpersulfuric acid, perboric acid, peracetic acid, etc. Compo,undsisuchasdiazodiisopropyl nitrile, sodium perborate, acetyl .peroxide, ammoniumpersulfate, potassium persulfate, hydrogen ,peroxide, ceric sulfate etc.are;illustrativeof the catalysts that mayrbe used. Such compounds arefree=radical producing catalysts. The amount of catalyst may be variedwithin the limits of from about 0.001 to 0.5 part of catalyst per 100parts of monomer mixture.

If desired, other conventional modifiers such as reducin g agents,shortstop s,etc. may be added-to the polymerization medium to regulatethe molecular weight of the copolymer and direct :the course of thereaction.

' Inorder to prepare "the acrylonitrile-vinyl sulfo-namide copolymers ofthe present invention, it is necessary that the reaction be carried outat a pH of from about 3.0 to 8.0. Outside of 'thispI-I range,undesirable side reactions .occur and, as ,a result, substantially noneof the vinyl sulfonamide will copolymerize with the acrylonitrile. Whenmaterials otherithan vinyl :sulfonamide, acrylonitrile and the catalystarepresent in the reaction medium, as for example when ,an emulsifyingagent is present, it is frequently necessary to positively control thepH through the use of asuitablezbulfer.

The copolymers ,of this invention contain from 1 to 15 partsby weight ofvinyl sulfonamide and correspondingly from 99 :to ;-parts by weight ofacrylonitrile. The copolymers are especially useful for the preparationof fibers and filaments sby extruding an organic solvent solutionthereof into a-coagulant suchas water, or into an evaporative.atmospheresuchas air, nitrogen, steam, etc. The filaments :so formed may bestretched while still soft or through an after-softening treatment toorient the copolymer and increase its ,tensiles-trength. The organicsolvent solutions may also be ,used-to prepare films by casting methodand they are valuableas an ingredient in coating compositions.

The tensile strength and heat distortion temperature of filaments andfibers formed from the copolymers of the presentinventionmay be greatlyincreased by crosslinking the copolymers with formaldehyde, a polymerthereof, ,or hexamethylene tetramine. The acrylonitrilevinyl sulfonamidecopolymers may be treated with such .crosselinkingagents either beforeor after filaments have been formed. The manner in which this may beaccomplished-.isgmore completely set forth in co-pending application,;Se1;i al No. 333,345 filed January 26, 1953, now abandoned, inthe1-name of Harold F. Park, wherein the process for crossdinking vinylsulfonamide polymers is claimed and/more completely described.

One of the most valuable properties of the fibers prepared from thecopolymers of the present invention is that they can be .dyed with alarge number of acid, alkaline and substantive dyes by coupling the dyesdirectly to thesulfonamidegroups. Cross-linking does not materiallyaffect the dyeability of fibers formed from the copolymers. The colorsobtained as a result of the coupling .reactionare particularly fast tolaundering.

. Example V sodium=sulfitesolution. Boil for 10 minutes and remove thefibers. Wash the fibers with distilled water and dry.

The ifibers derived from 'the acrylonitrile-vinyl sulfonamide copolymers:are dyed intensely blue whereas the 5 6 fibers derived frompolyacrylonitrile are substantially References Cited in the file of thispatent unafiected by the treatment, having only a slight blue tingeUNITED STATES PATENTS What is claimed is: 2,324,896 Zerweck July 20,1943 1. A copolyrner of from 85 to 99 parts of acrylonitrile 5 2,464,120Dickey Mar. 8, 1949 and from 15 to 1 parts of vinyl sulfonamide.

2. A copolymer of 90 parts of acrylonitrile and 10 FOREIGN PATENTS partsof vinyl sulfonamide. 878 568 F Oct. 19 1942 3. A synthetic fiberconsisting essentially of a co- 3 rance polymer of from 85 to 99 partsof acrylonitrile and from 10 15 to 1 parts of vinyl sulfonamide.

1. A COPOLYMER OF FROM 85 TO 99 PARTS OF ACRYLONITRILE AND FROM 15 TO 1PARTS OF VINYL SULFONAMIDE.